首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1028篇
  免费   43篇
  国内免费   76篇
林业   45篇
农学   170篇
基础科学   27篇
  38篇
综合类   407篇
农作物   109篇
水产渔业   40篇
畜牧兽医   202篇
园艺   37篇
植物保护   72篇
  2024年   1篇
  2023年   9篇
  2022年   20篇
  2021年   23篇
  2020年   33篇
  2019年   35篇
  2018年   18篇
  2017年   42篇
  2016年   42篇
  2015年   43篇
  2014年   48篇
  2013年   51篇
  2012年   74篇
  2011年   66篇
  2010年   72篇
  2009年   53篇
  2008年   58篇
  2007年   49篇
  2006年   40篇
  2005年   29篇
  2004年   32篇
  2003年   25篇
  2002年   18篇
  2001年   29篇
  2000年   20篇
  1999年   15篇
  1998年   17篇
  1997年   13篇
  1996年   14篇
  1995年   20篇
  1994年   23篇
  1993年   24篇
  1992年   14篇
  1991年   16篇
  1990年   6篇
  1989年   16篇
  1988年   10篇
  1987年   6篇
  1986年   5篇
  1985年   6篇
  1983年   2篇
  1982年   2篇
  1981年   2篇
  1980年   2篇
  1979年   2篇
  1978年   1篇
  1956年   1篇
排序方式: 共有1147条查询结果,搜索用时 15 毫秒
21.
AIM: To investigate the mechanism of the radiosensitizing effect of maximum non-cytotoxic doses of tetrandrine (Tet) on nasopharyngeal carcinoma cell lines CNE1 and CNE2.METHODS: The cells were treated with ma-ximum non-cytotoxic doses of Tet (for CNE1 cells at 1.5 μmol/L and for CNE2 cells at 1.8 μmol/L), irradiation at 4 Gy, or combination of irradiation and maximum non-cytotoxic doses of Tet. The cell cycle distribution was analyzed by flow cytometry. The protein levels of γ-H2AX, cleaved caspase-3, p-CDC25C, CDK1, p-CDK1, cyclin B1, ERK and p-ERK were determined by Western blot.RESULTS: The expression of γ-H2AX was increased in CNE1 cells and CNE2 cells after combined treatment with irradiation and maximum non-cytotoxic doses of Tet. The percentages of CNE1 cells and CNE2 cells at G2/M phase in irradiation group were (18.09±0.42)% and (18.48±1.32)%, respectively, which were decreased to (15.88±1.04)% and (13.80±0.82)% in combined treatment group, respectively (P<0.05). Combined treatment enhanced the increase in the protein level of cleaved caspase-3 caused by irradiation. The protein levels of p-CDC25C and p-CDK1 were increased in a dose-dependent manner by Tet treatment (P<0.05), while the expression of CDK1 showed no difference among different doses of Tet treatments. The protein levels of p-CDC25C, p-CDK1 and CDK1 showed no difference after the treatment with maximum non-cytotoxic doses of Tet. The combined treatment with irradiation and the maximum non-cytotoxic doses of Tet decreased the protein levels of p-CDC25C and p-CDK1 (P<0.05), increased the expression of cyclin B1, and had no influence on the expression of CDK1 (P<0.05). The combined treatment resulted in an increase in the protein level of p-ERK1 (P<0.05).CONCLUSION: The maximum non-cytotoxic doses of Tet enhance the DNA damage and apoptosis in CNE1 cells and CNE2 cells caused by irradiation, and the mechanism might be associated with ending of G2/M arrest via activation of ERK/CDC25C/CDK1/cyclin B1 pathways.  相似文献   
22.
菌核病是一类非专一性的植物真菌病原菌,寄主范围广泛,严重危害农作物的生产。对高世代重组自交系群体(RIL)及F2群体终花期茎秆进行菌核病抗性接种鉴定,根据构建的近红外模型对接种鉴定的茎秆木质素含量、单体组分比例进行测定,并进行相关性分析和QTL定位。结果表明在2013年和2014年RIL群体茎秆菌斑大小与木质素含量呈极显著负相关,相关系数分别为–0.348和–0.286,与单体G/S呈显著正相关,相关系数分别为0.198和0.167。2014年F2群体菌斑大小与木质素含量呈极显著负相关,相关系数为–0.306,与单体G/S相关性为0.142。F2:3家系抗(感)植株茎部切片间苯三酚染色观察表明抗性较强的材料木质素含量高于抗性较弱的材料。根据已构建的重组自交系高密度SNP遗传图谱,利用复合区间作图法对上述性状进行QTL分析,共检测到18个QTL,其中9个菌核病抗性相关QTL分布于A05、A06、C04和C06染色体,单个QTL可解释的表型变异为2.38%~12.05%;3个木质素含量QTL分别位于A04、A05和C01染色体,单个QTL可解释表型变异的2.03%~13.75%。6个木质素单体G/S QTL分布于A08、C03和C07染色体,单个QTL可解释表型变异的2.06%~8.66%。本文研究结果为油菜菌核病抗性育种提供了新的思路和理论基础。  相似文献   
23.
Septoria leaf blotch progresses rapidly, leading to the development of Zymoseptoria titici forms resistant to fungicides. Cephalosporium stripe is caused by Cephalosporium gramineum. The aim of this study was to evaluate the effectiveness of selected pesticides in limiting the symptoms of both diseases on winter wheat leaves, and to determine their influence on grain yield and the content and composition of protein fractions in wheat kernels. Propiconazoles were most effective in inhibiting the development of Septoria leaf blotch (symptoms were reduced from 54.7% to 78.6%). Strobilurins were less effective due to the presence of isolates with the G143A mutation. Symptoms of Cephalosporium stripe were rarely observed, and protective treatments did not reduce their severity. The highest content of grain protein (14.81%) was found in plants most intensely protected with the fungicides containing fenpropimorph, pyraclostrobin and epoxiconazole. The principal component analysis revealed that the plant protection method influenced the grain protein profile. The accumulation of HMW glutenins and α/β gliadins was mutually interrelated and higher in high-input treatments; control grain was characterized by close relationships between ω-gliadins, LMW glutenins, albumins and globulins, whereas low-input treatments influenced mostly γ-gliadins.  相似文献   
24.
AIM:To study whether homocysteine (Hcy) inhibits the expression of ATP-binding cassette transporter A1 (ABCA1) and ATP-binding cassette transporter G1 (ABCG1) by microRNA-33 (miRNA-33) signaling, and reduces the efficiency of reverse cholesterol transport (RCT).METHODS:RAW264.7 macrophages were induced by oxidized low-density lipoprotein (ox-LDL) to establish foam cell model. Oil red O staining was used to determine whether the model was established successfully. miRNA-33 mimics and miRNA-33 inhibitor were transfected into the cells by Lipofectamine 2000, and the cells were exposed to Hcy at concentration of 5 mmol/L for 24 h. The intracellular lipid droplets were observed by Oil red O staining. The expression of ABCA1 and ABCG1 at mRNA and protein levels was determined by real-time PCR and Western blot. The cellular cholesterol content was analyzed by HPLC, and effluent rate of cholesterol was detected by the method of liquid scintillation counting.RESULTS:Compared with blank control group, the lipid content in miRNA-33 mimics group was increased, and the expression of ABCA1 and ABCG1 at mRNA and protein levels was decreased (P<0.05). The intracellular cholesterol content was increased gradually (P<0.05), and the cellular cholesterol efflux rate was gradually decreased (P<0.05) in miRNA-33 mimics group. Compared with blank control group, the testing results in miRNA-33 inhibitor group were the opposition of those in miRNA-33 mimics group (P<0.05). No diffe-rence of the above indexes among blank control group, miRNA-33 mimics-NC group and miRNA-33 inhibitor-NC group was observed.CONCLUSION:Hcy inhibits the mRNA and protein expression of ABCA1 and ABCG1 through miRNA-33 signaling, and reduces the efficiency of RCT in RAW264.7 macrophage-derived foam cells.  相似文献   
25.
水稻镉积累与调控研究进展   总被引:3,自引:1,他引:3  
镉通过水稻植株吸收进入食物链而危害人畜健康,水稻低镉累积研究已成为当今生态环境领域、水稻栽培与育种领域的重要课题。本文从水稻对镉的积累累积特性、镉的运转、稻田镉的控制及低镉低累积积累水稻品种的选育等方面,综述了镉在不同水稻品种类型、不同生育期及不同水稻器官间的积累累积规律,镉从土壤到籽粒的运转过程,主要控镉技术对水稻镉吸收的影响,以及低镉低累积积累水稻品种选育的研究进展。并从水稻镉代谢规律与遗传改良、土壤修复、良种良法等方面探讨水稻低镉低累积积累的研究方向。  相似文献   
26.
农产品视频履历追溯系统设计   总被引:1,自引:0,他引:1  
针对目前农产品追溯系统中履历信息单一化和信息量少的问题,设计了一个以实现生产过程中质量追溯为目的的农产品视频履历追溯系统.基于ARM9嵌入式技术与H.264压缩技术相结合对农产品生产过程进行视频履历的采集和压缩处理,应用3G无线传输技术对视频履历进行传输,通过生产服务器对视频履历进行存储,以.NET为平台开发了用户对农产品视频履历追溯系统的软件.该系统可采集农产品生产过程各个阶段的视频履历,为农产品追溯提供了更直观、更丰富、更具说服力的履历信息.该系统运行结果表明,系统具有通用性强、可靠性高、稳定性好、便携式等特点,可方便地应用于温室、农田等各种农产品生产的环境,从而满足用户的不同需求.  相似文献   
27.
板栗疫病菌一低毒病毒系统.是一个优良的研究植物病原真菌致病和病毒一宿主相互作用分子机制的模型。随着研究的深入,原有的苯菌灵和潮霉素两个遗传转化筛选标记已不能满足研究需要。文章报道构建一个由构巢曲trpC启动子驱动的G418抗性Neo基因盒,并成功应用于板栗疫病菌的遗传转化研究。  相似文献   
28.
长沙黑麋峰冬季鸟类资源调查及多样性分析   总被引:3,自引:0,他引:3  
通过对黑麋峰森林公园鸟类资源的初步调查,共鉴定鸟类28种,隶属于5个目,15个科,25个属。公园内的Shannon-Wiener指数为0.864 6,均匀度指数为0.597 5。同时,用G-F指数对该地区鸟类的科与属的多样性指数进行了分析,得出G指数为1.374 5,F指数为1.586 2,G-F指数为0.133 5。与湖南其它几个地区的鸟类多样性相比,黑麋峰的鸟类多样性较低,并进一步分析了其鸟类多样性低的原因。  相似文献   
29.
随着社会现代化的不断发展,越来越多的高新技术逐步问世,例如:云计算、大数据、人工智能、5G技术等.5G技术出现给人们生活带来了便利,同时也为各个产业的发展提供了强大动力.5G推动下的农业现代化发展就是结合5G技术当前发展状况和我国现阶段的农业现状,利用先进技术推动农业各方面发展进程.本文从"5G+农业"的角度出发,分析...  相似文献   
30.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号